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Feb. 7, 1956 H. F. ENGELMAN-N ET AL 2,734,170

CRYSTALA HOLDER Filed June 22. 1951 OUTPUT many/f United States Patent() CRYSTAL HOLDER Herbert F. Engelmann, Mountain Lakes, N. J., and John A. Kostriza, New Dorp, N. Y., assignors to International Telephone and Telegraph Corporation, a corporation of Maryland Application June 22, 1951, Serial No. 233,052

2 Claims. (Cl. S33- 6) This invention relates to ultra high frequency apparatus and more particularly to devices for holding crystals in coupled relation with microwave transmission circuitry.

In the copending application of D. D. Grieg-H. F. Engelmann, Serial No. 227,896, tiled May 23, 1951, a new type ofmicrowave transmission system is disclosed with which the crystal holders of this invention are particularly applicable. The new system employs, usually, two conductors, one as a ground conductor and the other as a line conductor spaced close together in substantially parallel relation. The so-called ground conductor, which may be at ground potential or some other given potential, is considerably wider than the line conductor so that the surface thereof provides in effect an image reflection of the line conductor, whereby the distribution of the electric and magnetic fields between the conductors is substantially the same as the distribution between one conductor and the neutral plane of a twoconductor parallel system. Small variations in size and shape of the line conductor may produce variations in the characteristic impedance of the system but the eld distribution with respect to the ground conductor is not materially disturbed. Likewise, certain variations in the surface of the ground conductor do not materially disturb the field distribution with respect to the surface thereof since such variations either neutralize each other or do not adversely aiect the eld distribution between the two conductors. Bythis system, microwaves can be easily propagated by the TEM mode along the line-ground conductor system since the microwaves ow in the regions of the electromagnetic eld bounded substantially by the opposed surfaces of the line and ground conductors. This propagation of microwave energy takes place regardless of whether or not the space between the two conductors is open or occupied by insulating material such as is the case where printed circuit techniques are used.

One of the objects of the invention is to provide a device to hold a crystal unit in coupled relation with a conductor of a microwave transmission system.

Another object of the invention is to provide an impedance matching relation between a coaxial line and, more particularly, a coaxial line form of crystal holder and theabove described line-ground conductor type of system.

One of the features of the invention is the means by which an impedance match is obtained between the crystal holder and the conductors of the line-ground conductor system. In one embodiment the impedance matching relation is obtained by counter-sinking with respect to the conductive surface of the ground conductor, the shell of the crystal. holder for axial coupling of the terminal of the crystal and the line conductor. This counter-sunk relationship is determined by the diiference, on the one hand of the size and spacing of the crystal holding shell and terminal, and on the other hand, of the size and spacing of the line-ground conductors. The difference in the shape of the holder shell and the ground conductor also presents a discontinuity, but this may be compensated 2,734,170 Patented Feb. 7, 1956 for by the provision of a body of dielectric material of proper size and dielectric characteristic disposed coaxially with respect to the terminal connection for the crystal.

Another feature of the invention is its adaptability for location at an angle ,to the line conductor. This angular coupling in .one form is obtained by providing an opening in the wide ground conductor with the shell of the holder disposed against the ground conductor in concentric relation to the opening so that the terminal of the crystal unit or an adapter therefore may extend through the opening to the line conductor. In this arrangement, a body of dielectric material may be disposed either as a bead or a layer between vthe line and ground conductors. Where the line and ground conductors are separated by a layer of insulation the line conductor may be extended beyond the connection to the crystal so as to provide a tuning stub for matching purposes. Another feature is to connect such a tuning stub to the ground conductor in such a manner as to form when required a direct current return path about the crystal.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, wherein:

Fig. l is a view in side elevation with parts broken away in section to show a crystal holding device in a.,- sociation with a line-ground conductor system;

Fig. 2 is a plan view of a line-ground conductor arrangement with a crystal holder indicated in broken lines disposed at right angles to the line conductor;

Fig. 3 is a sectional view taken along line 3-3 of Fig. 2 showing the angular positioning of the crystal holder;

Fig. 4 shows a variation that may be applied to the crystal arrangement of Fig. 3; and

Fig. 5 is a cross-sectional View similar to Fig. 3 showing the application of a crystal holder to a line-ground conductor system such as indicated in Fig. l.

Referring to Fig. l of the drawing, the microwave transmission system illustrated comprises a first or line conductor l and a second or ground conductor 2. The ground conductor is preferably of sheet or ribbon form, although other forms may be used, having a width considerably greater than the width of the line conductor 1. The conductor 2, for example, may comprise one of the walls of a chassis or other part of the electric apparatus with which or in which the transmission system is used. The ground conductor 2 mayextend a considerable distance laterally with respect to the line conductor but for practical purposes the width of the ground conductor may be twice or three times the width of the line conductor. The purpose of having the ground conductor of a width two to three times greater than the width of the line conductor is to provide in effect an image reflection of the line conductor so that the distribution of the electric and magnetic fields between the conductors is similar to the distribution between one conductor and the neutral plane of a two-conductor parallel system. By making the spacing between the two conductors small, for example, a fraction of the wavelength of the mid frequency of the microwave energy, the linx distribution is concentrated almost entirely between the opposed surface of the two conductors.

Microwave energy may be launched onto the lineground conductor system by any suitable means, a coaxial line 3, 4 being shown by way of illustration as one satisfactory form of launching device. Since the coaxial line coupling arrangements presents an impedance matching problem similar to that of the crystal holder, the principrles of this invention are applicable to both, The outer conductor 3 of the coaxial line is countersunk with respect to the upper surface of the conductor 2 so as to bring the inner conductor 4 into alignment with the line conductor 1. The reason for the counter-sinking is that the spacing between the conductors 1 and 2 for a given characteristic impedance is usually smaller than the spacing between the inner and outer conductors of the coaxial line of corresponding impedance. The outer conductor 3 is connected to ground conductor 2 as indicated at 5. Where the ground conductor 2 is of suicient thickness, it may be cut away to provide a recess 5 of suicient depth to receive the outer conductor 3 in desired coupled relation. The discontinuity between the shape of the outer conductor 3 and the ground conductor 2 may cause some perturbation of the waves. The dielectric bead 6 at the end of the coaxial line is so selected as to overcome the effects of this discontinuity.

The crystal holder comprises an outer cylindrical shell 7 of conductive material which corresponds to the outer conductor 3 of the coaxial line. For matching purposes the conductor 2 may be cut away to provide a recess S to receive the shell 7 in a coaxial relationship with respect to the line conductor 1. An insulating sleeve 9 is receivable in one end of the shell 7 so as to receive a crystal unit 10 in insulated supporting relation within the shell 7. Where the conductor 1 is of suiiicient size it may be provided with an axial opening 11 for socket reception of the terminal 12 of the crystal. The end of the shell 7 adjacent the terminal connection is provided with a bead of dielectric material 13 of sufficient dielectric characteristic to compensate for any mismatch present due to the discontinuity between the cylindrical shape of the shell 7 and the flat shape of the conductor 2.

The crystal may be coupled in circuit by connecting a line 15 to the end terminal 16 of the crystal 10 through a load resistor 17 and connection 13 to the line conductor 2 grounded at 19. The detected output across the resistor 17 is thus obtained by connection 20. The sleeve 9 is of such thickness and dielectric quality as to provide a bypass condenser for R. F. energy about the crystal unit 10.

Referring to Figs. 2 and 3 another embodiment of the invention is shown wherein the line-ground conductor arrangement is provided on a layer of insulation 21. The line conductor 22 is shown in the form of a flat ribbonlike conductor, while the ground conductor 23 is preferably in the form of a thin sheet of conductive material. The conductors 22 and 23 may be applied to the layer 21 in any known manner such as by one of several so called printed circuit techniques. The ground conductor 23 is provided with an opening 24 and the insulating layer 21 is likewise provided with an opening 25 which is coaxial with respect to the opening 24. The shell 26 which is provided with an end flange 27 is connected to the ground conductor Z3 in coaxial alignment with the openings 24 and 25. Disposed within these openings is a terminal connector or adapter 2.3 which contains an opening 29 in one end thereof to receive the terminal 12 of the crystal unit 10 While the other end 30 is adapted to be received in an opening 31 cut through the conductor 22. The end 30 is electrically connected to the conductor 22 by swedging it in the opening or by soldering. lf desired, the end 30 may be brazed or soldered direct to the line conductor. The shank of the connector 28 is provided with a circumferential flange or shoulder 32 which is adapted to position the connector against the insulating layer 21 during fabrication. A crystal holder was made in accordance with this embodiment for a crystal (type INZS-B) to operate in the 4700 mc. region. In operation with a resistance load of 100 ohms a rectied current of 0.5 ma. was obtained. The insulation 21 was 1A@ inch thick coated on both sides with copper about l mil. thick. The top coat of copper was partially removed leaving a strip 22 which was 0.220 inch wide.

In order to provide for impedance matching such as may be required due to the discontinuities presented by the shell 26 of the crystal holder and the terminal connector 28, the conductor 22 is extended beyond the terminal connection to provide a tuning stub 33. Where it is desirable to have a return path for direct current a connector clip or other connections 34 may be applied to connect the conductors 23 and 33 at a desired point out from the connection at 31. Such a connecting clip is illustrated in Fig. 4.

In Fig. 5 the crystal holder is shown applied to a spaced line-ground conductor arrangement similar to that of Fig. l. The ground conductor 2 is slightly indented as indicated at 3S and provided with an opening 36 for alignment with the interior of the crystal holder 37. The indentation 35 is provided to receive a bead of dielectric material 38 which may be used to at least partially support the conductor 1 but mainly to provide sufficient dielectric material coaxially of the terminal connector 39 for crystal i0 to compensate for any mismatch present due to the discontinuities of the cylindrical shape of the shell 37 and the terminal connection with respect to the shapes of the ground conductor 2 and line conductor 1. Means other than the indentation 35 may be employed for retention of the bead 38, for example, any suitable adhesive may be used. Also, the conductor 1 may be extended beyond the connector 39 for matching purposes, and this stub extension may also be connected to the ground conductor 2 as indicated at 41 to form a direct current return path with respect to crystal 40.

While we have described above the principles of our invention in connection with specic apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of our invention, as set forth in the objects thereof and in the accompanying claims.

We claim:

l. In a microwave transmission system, a planar sheet of solid dielectric material, a rst planar conductor lying at against and supported on one face of said sheet, a second planar conductor lying flat against and supported on the opposite face of said sheet, said conductors extending parallel to each other, said sheet spacing said conductors a small fraction of a wavelength apart, said second conductor being at least twice as wide as said rst conductor, a conductive cylinder disposed at right angles to said second conductor in conductive relation thereto, said second conductor and said dielectric sheet each having an opening therethrough coaxially of said cylinder, an inner conductor disposed axially of said cylinder and extending through said openings into conductive relation with respect to said first conductor, the distance between said second conductor and the inner conductor at the opening of said second conductor being less than the distance between the cylinder and said inner conductor.

2. In a microwave transmission system, a planar sheet of solid dielectric material, a rst planar conductor lying against one face of said sheet, a second planar conductor lying against the opposite face of said sheet, said conductors extending parallel to each other, said sheet spacing said conductors a small fraction of a Wavelength apart, said second conductor being at least twice as Wide as said tirst conductor; a coaxial line holder for coupling a crystal to said rst and second conductors, said holder comprising a conductive shell, a sleeve of insulation disposed in said shell to receive a crystal unit therein in spaced capacitance relation to said shell, said shell extending from said second conductor at right angles thereto in a direction away from said tirst conductor and being electrically connected to said second conductor, said second conductor and said dielectric sheet each having an opening therethrough, and a connecting conductor connected to said rst conductor and passing through the openings in the dielectric sheet and the second conductor for connecting a terminal of the crystal unit to said rst conductor, the distance between said second conductor and said connecting conductor at the opening of said second conductor being less than the distance between the shell and the connecting conductor within the shell.

References Cited in the le of this patent UNITED STATES PATENTS 6 Sharpless Mar. 30, 1948 Shanklin Aug. 2, 1949 Hunt Feb. 21, 1950 Harrison May 16, 1950 Salati Jan. 30, 1951 Noyes May 29, 1951 Rumsey July 8, 1952 Bliss Sept. 23, 1952. 

